Interesting

Snow Leopard 10.6.2 is out. An unlucky upgrader attempted to go 10.6.1 -> 10.6.2 and it hosed the machine. This required the upgrader to reinstall Snow Leopard from disk, then upgrading to 10.6.2. Backup your data before upgrading!

Redefining an aliased method may not do what you expect: When the aliased method is invoked the original implementation executes.